1. Field of the Invention
The present invention relates to an innovative azo dye compound, a colorant-containing curable composition suitable for forming color images and composing a color filter to be used for a liquid crystal display device or a solid state image pickup device, as well as a color filter using the colorant-containing curable composition and a production method of the same.
2. Description of the Related Art
In the field of dyes, it has been desired to develop compounds excellent in both light fastness and heat resistance, and investigations on the development thereof have enthusiastically been made. Particularly in the field of dyes that are soluble in solvents or water, compounds excellent in both light fastness and heat resistance have conventionally been desired. With respect to dyes excellent in both light fastness and heat resistance, phthalocyanines type compounds and Cr complexes of azo type dyes, etc. are known. However, since the phthalocyanine type compounds are unsuitable for absorption of visible light with wavelength of 400 to 500 nm, they are not useful for Yellow or Magenta dyes, and moreover, since the phthalocyanine type compounds have high light fastness due to molecular association, there is a problem of storage stability such that dyes are precipitated when dissolved in water or a solvent.
On the other hand, since the Cr complexes of azo type dyes contain a Cr atom, it has been pointed out before that they are harmful to the human body, living things, and the environments, and their improvement has urgently been desired. The azo type dyes are useful dyes which have high color value and are capable of absorbing light at various wavelengths, but non-metal complex type azo type dyes satisfying both high light fastness and heat resistance have not been developed yet.
Among them, compounds having γ-acid as a coupling component (e.g., Acid Red 57) and compounds having pyrazolone (e.g., Acid Yellow 29) have been previously known as azo dyes with relatively good light fastness, but compounds satisfying both high light fastness and heat resistance have not been developed yet (see Polish Patent No. 101,484, German Patent No. 2,714,204, and French Patent No. 2,303,839).
Further, these dyes have another problem in that their heat resistance and light fastness are considerably deteriorated depending on the conditions of use. For example, in cases where the types of fibers to be dyed are changed, where other dye compounds, photopolymerization initiators, polymer compounds, oxidizing agents/reducing agents, or the like coexist with these dyes, where they are used in ozone-generating environments, or where they are used in singlet oxygen-generating environments, at least one of heat resistance and light fastness is deteriorated.
As a method for producing a color filter to be used for a liquid crystal display device or a solid state image pickup device, a dying method, a printing method, an electrodeposition method, and a pigment dispersion method are known.
Among them, the pigment dispersion method is a method for producing a color filter by photolithography from colored radiosensitive compositions obtained by dispersing pigments in a variety of photosensitive compositions. In this method, obtained color filters are stable to light and heat since pigments are used, and they are provided with sufficient positioning precision since patterning is carried out by photolithography. Thus the method is suitable for producing a color filter for a high precision color display with a large size.
To produce such a color filter by the pigment dispersion method, a radiosensitive composition is applied to a substrate by a spin coater or a roll coater and dried to form a film, and the film is exposed to light and developed to obtain color pixels. These steps are repeated an appropriate number of times corresponding to the number of the hues, to obtain a color filter.
For the pigment dispersion method, negative type photosensitive compositions containing photopolymerizable monomers and photopolymerization initiators both together in alkali-soluble resins are disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 2-199403, 4-76062, 5-273411, 6-184482, and 7-140654). However, although further improved precision has recently been desired in a color filter for a solid state image pickup device, the resolution cannot be improved substantially since a pigment exists in the form of particles with a certain size in the case of employing a conventional pigment dispersion method, and also, color irregularities are caused due to bulky particles of the pigment. Thus, such a conventional pigment dispersion method is unsuitable for uses where fine patterns are required, such as in a solid state image pickup device,.
In order to achieve high image resolution, techniques in which dyes are used as the coloring materials have been investigated (see, for example, JP-A No. 6-75375). However, it has been found that a dye-containing curable composition has the following problems.
(1) It is difficult to obtain a liquid state curable composition having a desired spectrum since a conventional dye has a poor solubility in either an aqueous alkaline solution or an organic solvent (hereinafter, simply referred to as solvent in some cases).
(2) It is difficult to adjust the solubility (developing property) of cured parts and non-cured parts since most dyes interac with another component in the curable composition.
(3) A large quantity of a dye has to be added in the case where the molar extinction coefficient(ε) of the dye is low, and therefore a content of other components such as polymerizable compounds (monomers), a binder, a photopolymerization initiator and the like have to be reduced in the curable composition, resulting in deterioration of the curability and the post-curing heat resistance of the composition and the developing property of (non) cured parts.
(4) Dyes are, in general, inferior in light fastness and heat resistance to pigments.
Unlike in the case of use for producing a semiconductor device, in the case of use for producing a color filter for a solid state image pickup device, a film as thin as 1.5 μm or thinner is required. Accordingly, the curable composition is required to contain a large quantity of a dye resulting in the above-mentioned problems.
Meanwhile, a red color ink composition for a color filter obtained by dissolving a mono-azo type anionic red color dye in an aqueous amide type organic solvent solution has been disclosed (see, for example, JP-A No. 9-291241). However, the composition is insufficient in light fastness and heat resistance.
As described above, it has been difficult to achieve the performances required for use for high precision color filters particularly for solid state image pickup devices and the like. That is, it has been difficult to achieve sufficient fineness of color patterns, sufficient thinness of films, sufficient durability to light and heat, and sufficient developing property (pattern formability).